Compressors dimensional analysis

The scope of coverage includes internal flows of Newtonian and non-Newtonian incompressible fluids, adiabatic and isothermal compressible flows (up to sonic or choking conditions), two-phase (gas-liquid, solid-liquid, and gas-solid) flows, external flows (e.g., drag), and flow in porous media. Applications include dimensional analysis and scale-up, piping systems with fittings for Newtonian and non-Newtonian fluids (for unknown driving force, unknown flow rate, unknown diameter, or most economical diameter), compressible pipe flows up to choked flow, flow measurement and control, pumps, compressors, fluid-particle separation methods (e.g.,... 

Since the polytropic head has the same units as the pump head times the acceleration due to gravity, it follows that we may apply the dimensional analysis of Section 17.2 to the compressor as well as the pump, with H p replacing gH. This reveals the same independence of the specific volume of the fluid being passed, and the same dependence on volume flow rate at suction, Q, and speed, N. 

Dimensional analysis applied to compressor pressure ratio... 

Instead of considering polytropic head, it is possible to carry out an alternative dimensional analysis based on inlet and outlet pressures of a compressor section. We will begin by assuming that the compression process may be represented using the parameter set ... 

Compressor performance parameters follow basic dimensional analysis and similarity rules which allow to design and test stages at some reference conditions and then apply them at actual (dimensional) conditions. If it were 100% rigorously followed, this process would guarantee a perfect matching of the performance. Unfortunately, in real life this is not always possible for several reasons such as lirst and last stage effects, lateral injections, difSculty of matching Reynolds number, etc. Thus, some corrections are needed to move from the performance stored in the database to the actual machine. There is a trade-off between the complexity of the database and the amount of adaptations which are needed (Fig.14). 

Advanced two- and three-dimensional computer analysis methods are used today in the analyses of all critical components to verify aerodynamic, heat transfer, and mechanical performance. Additionally, the reduction of leakage paths in the compressor, as well as in the gas turbine expander, results in further plant efficiency improvements. At the compressor inlet, an advanced inlet flow design improves efficiency by reducing pressure loss. Rotor air cooler heat utilization and adt anccd blade and vane cooling arc also used. 

In order to size the compressor of a new refrigerator, it is desired to determine the rate of heat transfer from the kitchen air into the refrigerated space through the walls, door, and the top and bottom section of the refrigerator (Fig. 2-11). In your analysis, would you treat this as a transient or steady-state heat transfer problem Also, would you consider the heat transfer to be one-dimensional or multidimensional Explain. 

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